Interior device The evaporator coil fits In the furnace plenum. The plenum would be the section on the furnace on either aspect from the air handler, wherever air is brought in and despatched back out into your home. Seal up the outlet while in the wall applying increasing polyurethane foam. https://airconditionerinstallatio76429.blogolize.com/restaurant-and-bar-ventilation-no-further-a-mystery-68882585